Assessment of various pretreatment method on production of bioethanol followed by liquefaction of post hydrolysis residue

Abstract

The rise in energy demand due to increase in usage of transport, electricity and combustion squeezes the world s resources for both fossil fuels and renewable energy. In response to that, this research study focusses on the utilisation of lignocellulosic (Pithecellobium dulce leaf and Moringa olefira leaf) and non-lignocellulosic (Ulva lactuca and Gracilaria edulis) biomass for the simultaneous production of bioethanol and bio-oil, thereby creating an economic process involving the synthesis of two valuable liquid biofuels. newlineIn this study, the intensification of bioethanol production from lignocellulosic and non-lignocellulosic biomass via various optimized pretreatment methods as well as the valorization of energy from post-hydrolysis residue through hydrothermal liquefaction were explored. Prior to the pretreatment techniques, the feedstocks were characterised to understand its influence over the product yield. Among lignocellulosic biomass, P. dulcerecorded higher carbohydrate content (49.64%) compared to M. olefira (46.8%). Similarly, among non-lignocellulosic biomass, U. lactuca was observed to be rich in carbohydrates more than G. edulis by a small margin (61.38 % and 58.41 % respectively). These findings suggests that both lignocellulosic and non-lignocellulosic has sufficient carbohydrate for the production of bioethanol. Secondly, biomass samples were subjected to acid pre-treatment and alkali pre-treatment. The procedure was repeated with sonication included for more enhancement, thus subjecting the samples to four different enhancement methods.Both lignocellulosic and non-lignocellulosic feedstock was pretreated using HCl for acid pretreatment. Studies were conducted to estimate the influence of parameter such as acid concentration (1% , 2%, 3% and 4% v/v) and retention time (30, 60 and 90 min) on glucose and other sugar release. In order to highlight the influence of sonication time (1, 3, 5, 7 and 9 min), the acid treatment assisted with sonication were also performed. These pretreatment goals were to solubilize hemicellulose and lignin fraction, while retaining glucose content in the pretreated solids. Lower glucose release and higher other sugar release was observed for P. dulce (8.47% and 18.96%) and U. lactuca(9.21% and 23.06%) while using 2% v/v of HCl concentration at 60 min retention time under the sonication for 5 min. newline